As a wheel-driven vehicle, there is known an elevating work vehicle in which the vehicle main body is attached with, for example, a work table via elevation means. There are various types of such elevating work vehicles, among which relatively small vehicles are provided with a vertical elevating device (an expansion post, scissors mechanism, or the like) and a work table is attached to this vertical elevating device. Such elevating work vehicle is designed so that an operator on the work table can operate, from the work table, a drive of the vehicle and elevation of the work table (see, for example, Japanese Patent Application Laid-Open No. H10-158000 and Japanese Patent Application Laid-Open No. 2001-180899).
The operation of a drive of a vehicle in the above-mentioned type of work table is performed by the operator operating drive stop operation means (comprising, for example, a lever, a dial, and the like) for switching between starting and stopping and between a forward movement and a backward movement of the vehicle, and steering the vehicle, i.e. operating steering operation means (comprising, for example, a lever, a dial and the like). When the vehicle is steered by the operator while the vehicle is moving, the controller, which is provided on the work table or the vehicle, actuates a steering actuator (normal hydraulic cylinder) so that the steering angle of steering wheels detected by a steering angle detector becomes the target steering angle of the steering wheels which is set in accordance with an operational state of the steering operation means, and changes the steering angle of the steering wheels by means of a link mechanism (steering link mechanism). It should be noted here that “steering angle of the steering wheels” means a deflection angle of the steering wheels with respect to the front and rear central axes of the vehicle.
In the above work vehicle, the traveling speed of the vehicle can be changed by adjusting the operation condition of the travel stop operation means. However, when setting the target steering angle large (setting the target steering angle to a large value) while the vehicle is moving straight, and shifting to a rotating movement with a small curvature radius, the steering angle of the steering wheels cannot follow the target steering angle unless the operator reduces the traveling speed consciously, thus the vehicular trajectory deviates sharply from the target trajectory. Therefore, in the present work vehicle, when the target steering angle is changed to a large value while the vehicle is moving, the traveling speed of the vehicle is regulated to a predetermined speed or lower (or forcibly reduced depending on the traveling speed before steering is performed).